U.S. patent application number 09/901108 was filed with the patent office on 2002-02-21 for curable fluoropolyether rubber compositions.
This patent application is currently assigned to Shin-Etsu Chemical Co., Ltd.. Invention is credited to Koike, Noriyuki, Matsuda, Takashi, Sato, Shinichi.
Application Number | 20020022685 09/901108 |
Document ID | / |
Family ID | 18705183 |
Filed Date | 2002-02-21 |
United States Patent
Application |
20020022685 |
Kind Code |
A1 |
Matsuda, Takashi ; et
al. |
February 21, 2002 |
Curable fluoropolyether rubber compositions
Abstract
A fluoropolyether rubber composition comprising (A) a linear
fluoropolyether compound containing at least two alkenyl groups and
having a perfluoroalkyl ether structure in its backbone, (B) an
organosilicon compound having at least two silicon atom-bound
hydrogen atoms which all form H--Si(C.sub.aH.sub.2a)Si structures
wherein "a" is 1, 2 or 3, (C) a hydrosilylation catalyst, and (D)
an antidegradant, typically an aromatic secondary amine compound is
curable into products having heat resistance, chemical resistance,
solvent resistance, parting property, water repellency, oil
repellency, and weather resistance as well as resistance to acid,
alkali and oxidative degradation.
Inventors: |
Matsuda, Takashi; (Usui-gun,
JP) ; Sato, Shinichi; (Usui-gun, JP) ; Koike,
Noriyuki; (Usui-gun, JP) |
Correspondence
Address: |
MILLEN, WHITE, ZELANO & BRANIGAN, P.C.
2200 CLARENDON BLVD.
SUITE 1400
ARLINGTON
VA
22201
US
|
Assignee: |
Shin-Etsu Chemical Co.,
Ltd.
6-1, Otemachi, 2-chome, Chiyoda-ku
Tokyo
JP
|
Family ID: |
18705183 |
Appl. No.: |
09/901108 |
Filed: |
July 10, 2001 |
Current U.S.
Class: |
524/492 ;
524/544 |
Current CPC
Class: |
C08K 5/54 20130101; C08G
65/336 20130101; C08G 65/007 20130101; C08F 8/42 20130101; C08L
71/00 20130101; C08F 14/18 20130101; C08F 8/42 20130101; C08K 5/54
20130101 |
Class at
Publication: |
524/492 ;
524/544 |
International
Class: |
C08L 001/00; C08J
003/00; C08K 003/34; C08K 003/00; C08L 027/12 |
Foreign Application Data
Date |
Code |
Application Number |
Jul 10, 2000 |
JP |
2000-208633 |
Claims
1. A curable fluoropolyether rubber composition comprising (A) a
linear fluoropolyether compound containing at least two alkenyl
groups in a molecule and having a perfluoroalkyl ether structure in
its backbone, (B) an organosilicon compound having at least two
hydrogen atoms each bound to a silicon atom in a molecule, all the
silicon atom-bound hydrogen atoms forming H--Si(C.sub.aH.sub.2a)Si
structures wherein "a" is an integer of 1 to 3, (C) a
hydrosilylation catalyst, and (D) an antidegradant.
2. The composition of claim 1 wherein the linear fluoropolyether
compound (A) has the following general formula (1) or (2):
CH.sub.2.dbd.CH--(X).su- b.p--Rf'--(X).sub.p--CH.dbd.CH.sub.2 (1)
CH.sub.2.dbd.CH--(X).sub.p--Q--R- f'--Q--(X).sub.p--CH.dbd.CH.sub.2
(2)wherein X is independently --CH.sub.2--, --CH.sub.2O-- or
--Y--NR'--CO-- wherein Y is --CH.sub.2-- or a group of the
following structural formula (I): 19and R' is hydrogen, methyl,
phenyl or allyl, Q is a divalent hydrocarbon group having 1 to 15
carbon atoms, which may contain an ether bond, Rf' is a divalent
perfluoroalkylene or perfluorooxyalkylene group, and p is
independently equal to 0 or 1.
3. The composition of claim 1 wherein the linear fluoropolyether
compound (A) has the following general formula (3): 20wherein X is
independently --CH.sub.2--, --CH.sub.2O-- or --Y--NR'--CO-- wherein
Y is --CH.sub.2-- or a group of the following structural formula:
21and R' is hydrogen, methyl, phenyl or allyl, p is independently
equal to 0 or 1, r is an integer of 2 to 6, u is an integer of 1 to
6, and m and n each are an integer of 0 to 200.
4. The composition of claim 1 wherein the organosilicon compound
(B) has the following general formula (4): 22wherein R which may be
the same or different is a monovalent hydrocarbon group having 1 to
20 carbon atoms, Z is hydrogen or a mono- or divalent group of the
formula: --R, --M, --Q--Rf, --Q--, --Rf'-- or --Q--Rf'--Q-- wherein
Q is a divalent hydrocarbon group having 1 to 15 carbon atoms,
which may contain an ether bond, amide bond or carbonyl bond, Rf is
a monovalent perfluoroalkyl or perfluorooxyalkyl group, and Rf' is
a divalent perfluoroalkylene or perfluorooxyalkylene group, s and t
each are 1, 2 or 3, b and c each are 0 or 1, b and c are not 0 at
the same time, and "a" is 1, 2 or 3.
5. The composition of claim 1 wherein the antidegradant (D) is an
amine or phenolic compound.
6. The composition of claim 1 wherein the antidegradant (D) is an
aromatic secondary amine compound.
Description
[0001] This invention relates to a curable fluoropolyether rubber
composition which cures into products having heat resistance,
chemical resistance, solvent resistance, parting property, water
repellency, oil repellency, and weather resistance as well as
resistance to acid, alkali and oxidative degradation.
BACKGROUND OF THE INVENTION
[0002] Japanese Patent No. 2,990,646 discloses a composition
comprising a linear fluoropolyether compound containing at least
two alkenyl groups per molecule and having a perfluoropolyether
structure in its backbone, an organosilicon compound having at
least two H--SiOSi structures per molecule, and a hydrosilylation
catalyst. This composition cures into products having a good
profile of heat resistance, chemical resistance, solvent
resistance, parting property, water repellency, oil repellency, and
weather resistance.
[0003] Although such fluoropolyether rubber compositions exhibit
satisfactory performance in most applications, more acid resistance
is required in semiconductor and engine oil-related
applications.
SUMMARY OF THE INVENTION
[0004] An object of the invention is to provide a curable
fluoropolyether rubber composition which cures into products having
heat resistance, chemical resistance, solvent resistance, parting
property, water repellency, oil repellency, and weather resistance
as well as resistance to acid, alkali and oxidative
degradation.
[0005] We have found that a fluoropolyether rubber composition
obtained by blending (A) a linear fluoropolyether compound
containing at least two alkenyl groups and having a perfluoroalkyl
ether structure in its backbone, (B) an organosilicon compound
having at least two silicon atom-bound hydrogen atoms which all
form H--Si(C.sub.aH.sub.2a)Si structures, (C) a hydrosilylation
catalyst, and (D) an antidegradant is curable into products having
heat resistance, chemical resistance, solvent resistance, parting
property, water repellency, oil repellency, and weather resistance
as well as resistance to acid, alkali and oxidative
degradation.
[0006] The invention provides a curable fluoropolyether rubber
composition comprising
[0007] (A) a linear fluoropolyether compound containing at least
two alkenyl groups in a molecule and having a perfluoroalkyl ether
structure in its backbone,
[0008] (B) an organosilicon compound having at least two hydrogen
atoms each bound to a silicon atom in a molecule, all the silicon
atom-bound hydrogen atoms constituting a H--Si(C.sub.aH.sub.2a)Si
structure wherein "a" is an integer of 1 to 3,
[0009] (C) a hydrosilylation catalyst, and
[0010] (D) an antidegradant.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0011] The respective components of the curable fluoropolyether
rubber composition are described below.
[0012] The linear fluoropolyether compound (A) used herein is one
containing at least two alkenyl groups in a molecule and having a
divalent perfluoroalkyl ether structure in its backbone.
[0013] The perfluoroalkyl ether structure is a structure containing
a plurality of recurring units of the formula: --C.sub.dF.sub.2dO--
wherein d is independently on each occurrence an integer of 1 to 6.
Typical structure has the following general formula (5):
(C.sub.dF.sub.2dO).sub.q (5)
[0014] wherein q is an integer of 1 to 500, preferably 2 to 400,
more preferably 10 to 200.
[0015] Examples of the recurring units of formula (5) are shown
below.
--CF.sub.2O--, --CF.sub.2CF.sub.2O--,
--CF.sub.2CF.sub.2CF.sub.2O--,
--CH(CF.sub.3)CF.sub.2O--,
--CF.sub.2CF.sub.2CF.sub.2CF.sub.2O--,
--CF.sub.2CF.sub.2CF.sub.2CF.sub.2CF.sub.2CF.sub.2O--, and
--C(CF.sub.3).sub.2O--.
[0016] Of these, --CF.sub.2O--, --CF.sub.2CF.sub.2O--,
--CF.sub.2CF.sub.2CF.sub.2O--, and --CH(CF.sub.3)CF.sub.2O-- are
preferred. It is understood that the perfluoroalkyl ether structure
may consist of recurring units of one type or recurring units of
two or more types.
[0017] The alkenyl groups in the linear fluoropolyether compound
are those of 2 to 8 carbon atoms, especially 2 to 6 carbon atoms,
having a CH.sub.2.dbd.CH-- structure at an end such as vinyl,
allyl, propenyl, isopropenyl, butenyl and hexenyl, with the vinyl
and allyl being especially preferred. The alkenyl groups may be
present within the molecule, although they are preferably attached
to both ends of the molecular chain. In the preferred case, the
alkenyl groups may be attached either directly to both ends of the
backbone of the linear fluoropolyether compound or to the backbone
through a divalent linking group such as
--CH.sub.2--, --CH.sub.2O-- or --Y--NR'--CO--.
[0018] Herein Y is --CH.sub.2-- or a group of the following
structural formula (I): 1
[0019] (the bond may be at o, m or p-position) and R' is hydrogen,
methyl, phenyl or allyl.
[0020] Preferred linear fluoropolyether compounds (A) are those of
the following general formula (1) or (2).
CH.sub.2.dbd.CH--(X).sub.p--Rf'--(X).sub.p--CH.dbd.CH.sub.2 (1)
CH.sub.2.dbd.CH--(X).sub.p--Q--Rf'--Q--(X).sub.p--CH.dbd.CH.sub.2
(2)
[0021] Herein X is independently --CH.sub.2--, --CH.sub.2O-- or
--Y--NR'--CO-- wherein Y is --CH.sub.2-- or a group of the
following structural formula (I): 2
[0022] (the bond may be at o, m or p-position) and R' is hydrogen,
methyl, phenyl or allyl. Q is a divalent hydrocarbon group having 1
to 15 carbon atoms, which may contain an ether bond. Rf' is a
divalent perfluoroalkylene or perfluorooxyalkylene group, and p is
independently equal to 0 or 1.
[0023] Of these, fluoropolyether compounds of the following general
formula (3) are especially preferred. 3
[0024] Herein X is as defined above, p is independently equal to 0
or 1, r is an integer of 2 to 6, u is an integer of 1 to 6, and m
and n each are an integer of 0 to 200.
[0025] The linear fluoropolyether compound of formula (3) desirably
has a weight average molecular weight of about 400 to about
100,000, and especially about 1,000 to about 50,000.
[0026] Illustrative examples of the fluoropolyether compound of
formula (3) are given below. In the following formulae, m and n are
as defined above. 4
[0027] It is sometimes preferred to adjust the linear
fluoropolyether compound to a desired weight average molecular
weight for a particular application. In this case, a linear
fluoropolyether compound is subjected to hydrosilylation reaction
with an organosilicon compound having two SiH groups in a molecule
by a conventional method under ordinary conditions to give a
chain-lengthened product, which can be used as component (A).
[0028] The organosilicon compound (B) functions as a crosslinker
and chain extender for component (A). Any organosilicon compound is
useful as long as it has at least two hydrogen atoms each bound to
a silicon atom in a molecule, all the silicon atom-bound hydrogen
atoms forming H--Si(C.sub.aH.sub.2a)Si structures wherein "a" is an
integer of 1 to 3. Typical organosilicon compounds have the
following general formula (4). 5
[0029] Herein R which may be the same or different is a monovalent
hydrocarbon group having 1 to 20 carbon atoms. Z is hydrogen or a
mono- or divalent group of the formula: --R, --M, --Q--Rf, --Q--,
--Rf'-- or --Q--Rf'--Q-- wherein Q is a divalent hydrocarbon group
having 1 to 15 carbon atoms, which may contain an ether bond, amide
bond or carbonyl bond, Rf is a monovalent perfluoroalkyl or
perfluorooxyalkyl group, and Rf' is a divalent perfluoroalkylene or
perfluorooxyalkylene group. The subscripts "s" and "t" each are 1,
2 or 3, "b" and "c" each are 0 or 1, "b" and "c" are not 0 at the
same time, and "a" is 1, 2 or 3.
[0030] Examples of the monovalent hydrocarbon group represented by
R include alkyl groups such as methyl, ethyl and propyl and aryl
groups such as phenyl, although the detail of R will be described
later. Examples of the divalent hydrocarbon group represented by Q
include alkylene groups such as methylene, ethylene, propylene,
tetramethylene, and hexamethylene, arylene groups such as
phenylene, and combinations of alkylene groups with arylene groups.
These groups may contain ether, amide and carbonyl bonds.
[0031] Z is either a monovalent group (such as --H, --R, --M, or
--Q--Rf) or a divalent group (such as --Q--, --Rf'-- or
--Q--Rf'--Q--), which depends on the values of b and c.
[0032] Illustrative examples of the organosilicon compound of
formula (4) are given below. In the following formulae, Me is
methyl. 6
[0033] Note that "a" is an integer of 1 to 3 and k is an integer of
1 to 8.
[0034] With the compatibility with and dispersibility in component
(A), and uniformity after curing taken into account, organosilicon
compounds having at least one monovalent perfluoroalkyl group,
monovalent perfluorooxyalkyl group, divalent perfluoroalkylene
group or divalent perfluorooxyalkylene group are also useful.
[0035] The preferred perfluoroalkyl and perfluoroalkylene groups
are those of 1 to about 20 carbon atoms, and the preferred
perfluorooxyalkyl and perfluorooxyalkylene groups are those of 1 to
about 500 carbon atoms, especially 4 to about 500 carbon atoms.
[0036] The perfluoroalkyl, perfluorooxyalkyl, perfluoroalkylene and
perfluorooxyalkylene groups are exemplified by the groups of the
following general formulae. monovalent perfluoroalkyl groups:
C.sub.gF.sub.2g+1
[0037] g is an integer of 1 to 20, preferably 2 to 10. divalent
perfluoroalkylene groups:
--C.sub.gF.sub.2g--
[0038] g is an integer of 1 to 20, preferably 2 to 10. monovalent
perfluorooxyalkyl groups: 7
[0039] n is an integer of 1 to 5. divalent perfluorooxyalkylene
groups: 8
[0040] m+n is an integer of 2 to 100.
--(CF.sub.2O).sub.m--(CF.sub.2CF.sub.2O),--CF.sub.2--
[0041] m and n each are an integer of 1 to 50.
[0042] These perfluoro(oxy)alkyl and perfluoro(oxy)alkylene groups
each may be attached either directly to a silicon atom or to a
silicon atom through a divalent linking group. The divalent linking
group is an alkylene group, arylene group or a mixture thereof,
which may further have an ether bond oxygen atom, amide bond or
carbonyl bond. Such divalent linking groups of 2 to 12 carbon atoms
are preferred. Illustrative examples thereof include
--CH.sub.2CH.sub.2--, --CH.sub.2CH.sub.2CH.sub.2--,
--CH.sub.2CH.sub.2CH.sub.2OCH.sub.2--,
--CH.sub.2CH.sub.2CH.sub.2--NH--CO--,
--CH.sub.2CH.sub.2CH.sub.2--N(Ph)--C- O--,
--CH.sub.2CH.sub.2CH.sub.2--N(CH.sub.3)--CO--, and
--CH.sub.2CH.sub.2CH.su- b.2--O--CO--
[0043] wherein Ph is phenyl.
[0044] In addition to the monovalent organic group containing a
monovalent or divalent fluorinated substituent, that is, a
perfluoroalkyl, perfluorooxyalkyl, perfluoroalkylene or
perfluorooxyalkylene group, the organosilicon compound (B) may have
a monovalent substituent R attached to a silicon atom. Exemplary
monovalent substituents are substituted or unsubstituted
hydrocarbon groups of 1 to 20 carbon atoms including alkyl groups
such as methyl, ethyl, propyl, butyl, hexyl, cyclohexyl, octyl and
decyl; alkenyl groups such as vinyl and allyl; aryl groups such as
phenyl, tolyl, and naphthyl; aralkyl groups such as benzyl and
phenylethyl; and substituted ones of these groups in which some of
the hydrogen atoms are replaced by chlorine atoms, cyano groups or
the like, such as chloromethyl, chloropropyl, and cyanoethyl.
[0045] The organosilicon compound (B) may be cyclic, chainlike or
three-dimensional network. The number of silicon atoms per molecule
of the organosilicon compound is not critical although it desirably
has about 2 to about 60 silicon atoms, and especially about 3 to
about 30 silicon atoms.
[0046] Illustrative examples of the organosilicon compound are
given below. They may be used alone or in admixture of two or more.
In the formulae, Me is methyl and Ph is phenyl. 9
[0047] The organosilicon compound having hydrosilyl groups (B) is
preferably blended in such an amount that 0.5 to 5 mol, and more
preferably 1 to 2 mol of hydrosilyl groups (or SiH) groups may be
present per mol of alkenyl groups (e.g., vinyl, allyl or
cycloalkenyl) in component (A). Less amounts of component (B) may
achieve an insufficient degree of crosslinking. Excessive amounts
of component (B) may allow chain lengthening to become
preferential, inviting short cure, foaming, and losses of heat
resistance and compression set. The organosilicon compounds may be
used alone or in admixture of two or more.
[0048] The hydrosilylation catalyst (C) is preferably selected from
transition metals, for example, platinum group metals such as Pt,
Rh and Pd, and compounds of transition metals. Most of these
compounds are noble metal compounds which are expensive. Platinum
compounds are thus used because they are readily available.
Exemplary platinum compounds include chloroplatinic acid, complexes
of chloroplatinic acid with olefins such as ethylene, complexes of
chloroplatinic acid with alcohols and vinylsiloxanes, and platinum
supported on silica, alumina or carbon though not limited thereto.
Known platinum group metal compounds other than the platinum
compounds include rhodium, ruthenium, iridium, and palladium
compounds, for example, RhCl(PPh.sub.3).sub.3,
RhCl(CO)(PPh.sub.3).sub.2, RhCl(C.sub.2H.sub.4).sub.2,
Ru.sub.3(CO).sub.12, IrCl(CO)(PPh.sub.3).sub.2, and
Pd(PPh.sub.3).sub.4 wherein Ph denotes phenyl.
[0049] The amount of the catalyst used is not critical. A catalytic
amount can achieve a desired curing rate. From the economical
aspect and to obtain satisfactory cured products, the platinum
group metal compound is preferably added in an amount of about 0.1
to about 1,000 parts, more preferably about 0.1 to about 500 parts
by weight calculated as the platinum group metal per million parts
by weight of the entire curable composition.
[0050] The antidegradant (D), which is an agent for inhibiting
oxidative degradation, is selected from amine compounds, phenolic
compounds, sulfur compounds, phosphorus compounds, waxes, and metal
complexes thereof. The majority of these compounds are commercially
available. Any of commercially available antidegradants is often
used.
[0051] Examples of suitable amine antidegradants are shown below.
10
[0052] Examples of suitable phenolic antidegradants are shown
below. 11
[0053] Examples of suitable sulfur, phosphorus, metal complex and
combined antidegradants are shown below. 12
[0054] Of the foregoing antidegradants, amine and phenolic
antidegradants are preferred because most sulfur and
phosphorus-containing compounds can be a poison to the
hydrosilylation catalyst. Among others, aromatic secondary amine
compounds, that is, amine compounds in which substituents on the
amino group are both aromatic groups are most effective for
inhibiting oxidative degradation.
[0055] The antidegradant (D) is preferably added in an amount of
0.01 to 10% and more preferably 0.05 to 5% by weight based on the
composition of the invention. Outside the range, less amounts of
the antidegradant may be ineffective whereas excessive amounts can
affect the physical properties of cured rubber, for example,
lowering strength.
[0056] If desired, various additives may be added to the inventive
curable composition for improving its practical usage. For
instance, polysiloxanes containing CH.sub.2.dbd.CH(R)SiO units
wherein R is hydrogen or a substituted or unsubstituted monovalent
hydrocarbon group (see JP-B 48-10947) and acetylene compounds (see
U.S. Pat. No. 3,445,420 and JP-B 4-3774) are added for the purpose
of controlling the curing rate of the curable compositions. Other
useful additives are ionic compounds of heavy metals (see U.S. Pat.
No. 3,532,649).
[0057] To the curable composition of the invention, fillers may be
added for the purposes of reducing thermal shrinkage upon curing,
reducing the coefficient of thermal expansion of the cured
elastomer, improving thermal stability, weather resistance,
chemical resistance, flame retardance or mechanical strength,
and/or lowering the gas permeability. Exemplary additives include
fumed silica, quartz flour, glass fibers, carbon, metal oxides such
as iron oxide, titanium oxide and cerium oxide, and metal
carbonates such as calcium carbonate and magnesium carbonate. If
desired, suitable pigments and dyes are added.
[0058] The method of preparing the curable composition according to
the invention is not critical. The composition may be prepared
simply by mixing the above-described components. The composition
may be formulated as two parts, one part consisting of components
(A), (B) and (D) and the other part consisting of components (A)
and (C), which are to be combined together on use. For the
composition to cure, room temperature cure is possible depending on
the type of functional group in component (A) and the type of
catalyst (C) although a common, preferred practice is to heat the
composition at about 100 to 200.degree. C. for several minutes to
several hours for curing.
[0059] On use, depending on its particular application and purpose,
the curable composition may be dissolved in a suitable
fluorochemical solvent, for example, 1,3-bistrifluoromethylbenzene
or perfluorooctane in a desired concentration before it is
applied.
[0060] The curable fluoropolyether rubber composition cures into
parts which have good heat resistance, chemical resistance, solvent
resistance, parting property, water repellency, oil repellency and
weather resistance as well as improved resistance to acid, alkali
and oxidative degradation. The composition is thus useful in a
variety of molding applications, for example, as sealants for
semiconductor manufacturing apparatus, O-rings, diaphragms and
sealants for automobiles and aircraft, roll materials for copiers,
and electrode constituent materials for secondary cells and fuel
cells.
EXAMPLE
[0061] Examples of the invention are given below by way of
illustration and not by way of limitation. The viscosity is a
measurement at 25.degree. C. All parts are by weight.
Comparative Example 1
[0062] To 100 parts of a polymer of formula (6) below (viscosity
8,500 cs, average molecular weight 22,000, and vinyl content 0.009
mol/100 g) was added 20 parts of dimethylsiloxy-treated fumed
silica having a specific surface area of 200 m.sup.2/g. They were
mixed, heat treated and milled on a three-roll mill. To the mixture
were added 2.64 parts of a fluorinated organosilicon compound of
formula (7) below, 0.2 part of a toluene solution of a catalyst in
the form of chloroplatinic acid modified with
CH.sub.2.dbd.CHSiMe.sub.2OSiMe.sub.2CH.dbd.CH.sub.2 (platinum
concentration 1.0 wt %), and 0.4 part of a 50% toluene solution of
ethynyl cyclohexanol. They were mixed to give composition I. 13
[0063] The composition was deaerated in vacuum, placed in a
rectangular frame of 2 mm deep, deaerated again, and press cured at
100 kg/cm.sup.2 and 150.degree. C. for 10 minutes. From the cured
sample, a specimen was cut out and measured for physical properties
according to JIS K-6251 and 6253. The specimen was also examined
for chemical resistance and heat resistance in air. The results are
shown in Tables 1 and 2.
Comparative Example 2
[0064] Composition II was prepared as in Comparative Example 1
except that 2.49 parts of a fluorinated hydrogensiloxane of formula
(8) shown below was used instead of the fluorinated organosilicon
compound of formula (7). 14
[0065] As in Comparative Example 1, a cured sheet was obtained from
composition II. A specimen was cut therefrom and measured for
physical properties according to JIS K-6251 and 6253. The specimen
was also examined for chemical resistance and heat resistance in
air. The results are shown in Tables 1 and 2.
Example 1
[0066] Composition III was prepared as in Comparative Example 1
except that 1.0 part of an antidegradant as shown below was added
prior to the milling on the three-roll mill. 15
[0067] As in Comparative Example 1, a cured sheet was obtained from
composition III. A specimen was cut therefrom and measured for
physical properties according to JIS K-6251 and 6253. The specimen
was also examined for chemical resistance and heat resistance in
air. The results are shown in Tables 1 and 2.
Example 2
[0068] Composition IV was prepared as in Comparative Example 1
except that 1.0 part of an antidegradant as shown below was added
prior to the milling on the three-roll mill. 16
[0069] As in Comparative Example 1, a cured sheet was obtained from
composition IV. A specimen was cut therefrom and measured for
physical properties according to JIS K-6251 and 6253. The specimen
was also examined for chemical resistance and heat resistance in
air. The results are shown in Tables 1 and 2.
Example 3
[0070] Composition V was prepared as in Comparative Example 1
except that 1.0 part of an antidegradant shown below was added
prior to the milling on the three-roll mill. 17
[0071] As in Comparative Example 1, a cured sheet was obtained from
composition V. A specimen was cut therefrom and measured for
physical properties according to JIS K-6251 and 6253. The specimen
was also examined for chemical resistance and heat resistance in
air. The results are shown in Tables 1 and 2.
Example 4
[0072] Composition VI was prepared as in Comparative Example 1
except that 1.0 part of an antidegradant shown below was added
prior to the milling on the three-roll mill. 18
[0073] As in Comparative Example 1, a cured sheet was obtained from
composition VI. A specimen was cut therefrom and measured for
physical properties according to JIS K-6251 and 6253. The specimen
was also examined for chemical resistance and heat resistance in
air. The results are shown in Tables 1 and 2.
1TABLE 1 Chemical resistance (change of rubber hardness)
Comparative Example Example Chemcals 1 2 1 2 3 4 Initial 40 41 40
40 41 41 Conc. hydro- 42(+2) 48(+7) 42(+2) 42(+2) 44(+3) 44(+3)
chloric acid Conc. sul- 39(-1) 40(-1) 40(0) 40(0) 41(0) 42(+1)
furic acid Conc. hydro- 39(-1) 30(-11) 39(-1) 38(-2) 41(0) 41(0)
fluoric acid Tri- 38(-2) de- 38(-2) 38(-2) 40(-1) 41(0)
fluoroacetic composed acid 40% KOH 41(+1) 41(+1) 41(+1) 41(+1)
42(+1) 41(0) solution
[0074] Degrading conditions are immersion in the designated
chemical at 20.degree. C. for 3 days. Figures in parentheses denote
point increments or decrements from the initial.
[0075] Comparative Example 2 was less resistant to chemicals
because the crosslinking agent had a siloxane structure. All other
examples were fully resistant to chemicals.
2TABLE 2 Heat resistance in air Comparative Example Example 1 2 1 2
3 4 Hardness Initial 40 41 40 40 41 41 200.degree. C./ 38 (-2) 40
(-1) 39 (-1) 39 (-1) 43 (+2) 43 (+2) 7 days Elongation Initial 540
620 490 490 530 520 (%) 200.degree. C./ 7 days 450 (-17) 580 (-6)
440 (-10) 430 (-12) 500 (-6) 480 (-8) Tensile Initial 10.7 11.8 9.7
9.8 10.5 10.4 strength 200.degree. C./ 6.7 (-37) 11.0 (-7) 8.2
(-15) 8.0 (-18) 9.8 (-7) 9.4 (-10) (MPa) 7 days
[0076] Figures in parentheses denote point increments or decrements
from the initial for the hardness, and percent increments or
decrements from the initial for the elongation and tensile
strength.
[0077] Examples 1 to 4 corresponded to Comparative Example 1 to
which the antidegradants were added. As seen from Table 2,
Comparative Example 1 experienced substantial losses of rubber
physical properties, especially tensile strength, whereas those
compositions having antidegradants added experienced only some
losses of rubber physical properties. In particular, Examples 3 and
4 in which aromatic secondary amine compounds were used as the
antidegradant experienced a less reduction of rubber physical
properties. Comparative Example 2 in which the crosslinking agent
had a siloxane structure was more resistant to oxidative
degradation than Comparative Example 1.
[0078] It is evident from Tables 1 and 2 that the compositions
within the scope of the invention are improved in both chemical
resistance and oxidative degradation resistance.
[0079] Japanese Patent Application No. 2000-208633 is incorporated
herein by reference.
[0080] Although some preferred embodiments have been described,
many modifications and variations may be made thereto in light of
the above teachings. It is therefore to be understood that the
invention may be practiced otherwise than as specifically described
without departing from the scope of the appended claims.
* * * * *